Conventionally, an energy recovery system has been known to recover thermal energy in various facilities. As shown in FIG. 4, Patent Literature 1 discloses an exhaust heat recovery system as an exemplary energy recovery system to recover thermal energy of a diesel engine 500 on a vessel, and generate an electric power by utilizing the recovered thermal energy. The exhaust heat recovery system includes a first exhaust heat receiver 700 for heating an organic medium M by air cooling water W having flown out of an air cooler 600 for cooling compressed air A discharged from a supercharger 510 of the diesel engine 500, the organic medium M having a lower boiling point than the air cooling water W. After taking heat of the compressed air A in the air cooler 600, the air cooling water W takes heat of an exhaust gas G conveyed from the supercharger 510 to a chimney 800, and then, flows into the first exhaust heat receiver 700. In other words, the exhaust heat recovery system of Patent Literature 1 causes the air cooling water W to perform heat exchange with two heat mediums, that is, the compressed air A and the exhaust gas G, thereby heating the organic medium M by the air cooling water W having a temperature which has risen owing to the heat exchange. In this manner, the thermal energy of the diesel engine 500 is recovered by the means of the organic medium M.
The exhaust heat recovery system of Patent Literature 1 can recover the thermal energy of the two heat mediums, that is, the compressed air A and the exhaust gas G. However, the thermal energy is transferred to the organic medium M via the air cooling water W having a higher boiling point than the organic medium M. Hence, it is more difficult for this system to recover the sufficient thermal energy than a system where the thermal energy of the compressed air A and the exhaust gas G is directly taken by the organic medium M. Particularly, in a vessel mounted with an exhaust heat recovery system, for example, a diesel engine 500 will be appreciated to run at a low load to suppress fuel consumption. In this case, the thermal energy of the compressed air A that is taken by the air cooling water W becomes smaller, and thus it is even more difficult to recover the sufficient thermal energy.